Oil prospecting method



Patented Sept. 21, 1948 t 2,449,627 oILrRosPEo'rING ym'rnon 6 William J. Sweeney Summit, N lrassignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Original application Dece'mber 1.4. 1937, Serial No. 179,676. Dividedand-this'applieation August 9, 1941, Serial No. 406,226

The present invention is directed to a method for prospecting for oil and particularly to the type of method in which near surface gases are analyzed for constituents indicative of petroleum origin.

According to the present invention samples of near surface gases are obtained by collecting spaced samples of adsorbent material which have been exposed to such gases in their native environment and recovering the gas from said adsorbent material by desorption. This adsorbent material may be naturally occurring material or adsorbent material which is planted for the purpose at spaced points over the area to be explored.

One aspect of the present invention resides in a particular method for desorbing the adsorbent material involving the steps of chilling the material to a temperature below that of the lowest boiling constituent sought for, subjecting the sample to evacuation for a period sufiicient to 3 Claims. (Cl. 23 -230) purge the samples of constituents boiling below in an amount of at least ten parts in a million 3 and this concentration has significance in establishing the presence of petroleum deposits beneath the surface at which the gas sample is connected. A suitable analytical method which may be used for this purpose is that described and claimed in Patent 2,170,435 issued September 24, 1940.

When prospecting for oil by the method of the present invention, the samples of soil gas may be procured by any one of a number of methods. One of these methods is to suck the gas from a hole in the ground sealed from the atmosphere.

Another method is to place an absorbent material, such as active carbon, in a borehole sealed from the atmosphere, leave it there for a sufficient time for it to become saturated with the hydrocarbons in the soil gas and then withdraw it and recover the adsorbed hydrocarbons by evacuation or by treatment with steam or inert gas.

For the purpose of the present invention it is preferable to secure the moval of adsorbed gases from the soil itself. This removalcan be accomplished by any of the known methods referred to above. The samples of gas so obtained aremuch richer in hydroc ar bons than samples. obtained by mere suction from a borehole, since the latter are contaminated with. large quantities of air. A novel pro: cedure for obtaining anexcellent sample is to sorbed gases, pass the recovered gases through a train of adsorbing media for the removal therefrom of water vapor and carbon dioxide and. compress the purified sample into a preyiously.

evacuated absorption cell which is then directly examined in the spectroscope. It is advantageous in some cases to heat the soil sample during evacuation.

Another method for procuring a sample contemplated by the present invention is to place a sample of soil in a. suitable container chilled to such a point that methane only is removed under vacuum and subject it to evacuation. This operation will remove any adsorbed methane from the soil. When no more gas is recovered by evacuation at this temperature the temperature of the container can be raised to the boiling point of ethane and the evacuation repeated. If desired this procedure can be repeated for the recovery of propane and butane. The procedure can be simplified to suit the purpose of locating oil by following the methane removal step with an evacuation at the temperature of boiling propane or butane as desired. In' the latter case, ethane, propane and butane will be recovered. The sample recovered at this temperature must be subjected to dehydration before being examined in the spectroscope.

Some of the diluent effect of the methane can be avoided without resorting to refrigeration by collecting the soil sample at a depth adjacent to the uppermost water-table. This will usually be at least twenty feet below the surface of the ground and may be as deep as sixty feet. In this zone there is a tendency for the soil to adsorb higher hydrocarbons such as propane and butane to the exclusion of methane. With such a sample it may be possible to identify propane and/or butane by simply heating the sample and collecting and condensing the evolved vapors. Any condensible quantity of propane or higher hydrocarbon contained in such a sample is direct evidence of the existence of an 011 deposit at a lower level.

sample of soil gas by re- Other methods for obtaining a sample of soil gas include the evacuation or steaming of cores of soil obtained While drilling, boiling larg bodies of stagnant water, boiling samples of sub-surface water obtained in the area to be explored, and boiling or steaming samples of drilling mud used in the drilling of a well in the neighborhood under investigation. Still another method is to bore a hole in the ground, seal the top of the hole from the atmosphere, run a pipe through theseal to the bottom of the hole, feed in carbon dioxide, steam or other absorbable gas through this pipe 4 2. A method of geochemical oil prospecting comprising sinking a bore, disposing an adsorb.- ent for hydro-carbon gases therein in such relation to said bore that the gases in said bore have access to the adsorbent, removing saidadsorbent and analyzing the gases adsorbed for the presence of significant gases.

3. A method of geochemical oil prospecting comprising sinking a bore, disposing an active carbon therein in such relation to said bore that the gases in said bore have access to the active carbon, removing said active carbon and analyzand draw out gas from the hole through anotherpipe in the seal. The gases so recovered are passed through absorbing agents for carbon dioxide and water and the remaining permanent gase are utilized for examination according to the method of the present invention.

This application is a division of my copending application Serial No. 179,676, filed Dec. 14, 1937 and entitled Oil prospecting method, now abandoned.

The nature and objects of the present invention'having been thus described and illustrated,

ing gasesadsorbed thereby for the presence of significant gases.

WILLIAM J. SWEENEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 1 OTHER REFERENCES The on Weekly, August 1, 1938,'issue, pp.1s 

